4.Â Setting Up Journaling

4.1.Â Executing gjournal

Having prepared all the required partitions, it is quite easy
to configure journaling. We will need to switch to single user
mode, so login as root and type:

#shutdown now

Press Enter to get the default shell. We will need to unmount
the partitions that will be journaled, in our example
/usr and /var:

#umount /usr /var

Load the module required for journaling:

#gjournal load

Now, use your notes to determine which partition will be used
for each journal. In our example, /usr is
ad0s1f and its journal will be
ad0s1g, while
/var is ad0s1d and will
be journaled to ad0s1h.
The following commands are required:

Note:

If the last sector of either partition is used,
gjournal will return an error. You will have
to run the command using the -f flag to force an
overwrite, i.e.:

#gjournal label -f ad0s1d ad0s1h

Since this is a new installation, it is highly unlikely that
anything will be actually overwritten.

At this point, two new devices are created, namely
ad0s1d.journal and
ad0s1f.journal. These represent
the /var and /usr
partitions we have to mount. Before mounting, we must however set
the journal flag on them and clear the Soft Updates flag:

Warning:

Make sure the above entries are correct, or you will have
trouble starting up normally after you reboot!

Finally, edit /boot/loader.conf and add the
following line so the gjournal(8) module is loaded at every
boot:

geom_journal_load="YES"

Congratulations! Your system is now set for journaling. You can
either type exit to return to multi-user mode, or
reboot to test your configuration (recommended). During the boot you
will see messages like the following:

This usually means that gjournal(8) used the information in
the journal provider to return the file system to a consistent
state.

4.2.Â Journaling Newly Created Partitions

While the above procedure is necessary for journaling partitions
that already contain data, journaling an empty partition is somewhat
easier, since both the data and the journal provider can be stored
in the same partition. For example, assume a new disk was installed,
and a new partition /dev/ad1s1d
was created. Creating the journal would be as simple as:

#gjournal label ad1s1d

The journal size will be 1Â GB by default. You may adjust it by
using the -s option. The value can be given in
bytes, or appended by K, M or
G to denote Kilobytes, Megabytes or Gigabytes
respectively. Note that gjournal will not allow
you to create unsuitably small journal sizes.

For example, to create a 2Â GB journal, you could use the following
command:

#gjournal label -s 2G ad1s1d

You can then create a file system on your new partition, and
enable journaling using the -J option:

#newfs -J /dev/ad1s1d.journal

4.3.Â Building Journaling into Your Custom Kernel

If you do not wish to load geom_journal as a
module, you can build its functions right into your kernel. Edit your
custom kernel configuration file, and make sure it includes these two
lines:

options UFS_GJOURNAL # Note: This is already in GENERIC
options GEOM_JOURNAL # You will have to add this one